1. Field of the Invention
The invention relates to a goniometer, a system made of goniometer and observation device, and an initialization method for a goniometer.
2. Description of the Background Art
“Goniometer” designates a device, using which, on the one hand, angles are measurable and, on the other hand, the rotation of an object to a precise angle position can be carried out. The word “goniometer” is a composite term derived from the Greek words “gonio” (=angle) and “metron” (=to measure). Goniometer refers—as currently understood—to a device for the precise rotation of an object (observation device) around a fixed axis and a measurement of the angle assigned to the respective rotation. Goniometers are used in particular in conjunction with high-performance observation devices for military or geodetic purposes. It is important that the systems are handy, fast and simple to operate and as compact and light as possible. Goniometers are no be understood in the scope of the following description and therefore the present invention as robust devices, conceived for use in the field, in particular for determining azimuth angles of attached devices.
A tripod with tripod attachment is mentioned in this regard as a possible embodiment of a goniometer, whose vertical rotational axis (also designated as the standing axis in surveying) has an angle measurement which can be referenced to north. Various observation devices, for example, binoculars, monoculars, cameras, rangefinders, night vision devices, small weapons systems, etc., can be installed thereon. For example, these types of currently available observation devices can have—in addition to a daylight observation function—the following as further functions: target marking for military applications or for hunting purposes, integrated rangefinders and direction finders, an electronic display screen for providing information—in particular a display screen image being able to be overlaid with the daylight vision image, a night vision function, etc. It is thus possible, for example, to provide an image from a camera, location information in the form of a map, for example, measured distances or directions, stored information with respect to a target object being aimed at—e.g., vulnerability points of an enemy tank—or temperature and weather information to the user on the basis of the electronic display screen. In particular, these devices are often designed in the form of binoculars or field glasses, having the mentioned special functions for respective special usage purposes.
Information can be transmitted and linked between the devices, i.e., goniometer and observation device attached thereon, through corresponding data interfaces and, for example, a north-referenced azimuth alignment, which can be determined by means of sensors available in the device, can be used jointly with an elevation measurement and a distance measurement to determine target coordinates. The azimuth angle can be measured, e.g., by means of an angle encoder, which measures a respective angular position of a fixed base relative to a structure rotatable to the base. Furthermore, an elevation angle can be determined by a second angle encoder, which is arranged on a swivel joint on the structure, for example, or using an inclination sensor in the observation device. Furthermore, if the device location is known, for example, via GNSS (global navigation satellite system), e.g., GPS or Galileo, target coordinates can also be determined in a cartographic coordinate system.
For example, a magnetic compass alignment can be used to determine a north alignment of the goniometer. Especially in inside rooms of buildings, steel structures, tunnels, or in underground installations, and close to electrical facilities, however, a sufficiently precise magnetic compass measurement is often impossible. In particular, the material selection for the construction of a corresponding measuring device is restricted to those materials which are amagnetic and therefore do not influence the north determination.
For example, an observation device having a tripod implemented from amagnetic material for aiming at a target using a laser rangefinder and a digital magnetic compass is known from DE 10 2005 017 320 A1. The alignment of the arrangement relative to the north direction is determined here by means of the magnetic compass, which has three device-fixed magnetic field sensors.
In addition to finding north magnetically, finding north by determining the earth's rotational axis, which connects the geographic north pole and south pole by definition is also known. This principle has been known since the first construction of a Foucault's pendulum by John Bernard Léon Foucault in the year 1851.
The determination of the earth's rotational axis became technically usable above all by refinements in the field of gyroscopic sensors, beginning with spinning gyroscopes via laser ring gyroscopes and fibre gyroscopes up to the current MEMS gyroscopes (e.g., vibration gyroscope) which make a north determination able to be performed, for example, according to the HRG, principle (=hemispherical resonator gyroscope) or other known technologies. In contrast to the use of magnetic sensors, through the use of yaw rate sensors to determine north, for example, the tripod for an observation device or the goniometer, respectively, can also be manufactured from materials which have magnetic properties.
In this context, U.S. Pat. No. 5,272,922 discloses a gyroscope combined with a protractor for determining the geographic north pole, such a device being able to be used according to the disclosure in mining, surveying, or for target acquisition. Through this combination, the north direction can be specified as a reference and the angles determined by the protractor can be specified in relation to north.
To determine the geographic north pole relative to the base of the goniometer, for example, a simultaneous measurement can be performed using at least two gyroscopes arranged at an azimuth angle to one another or using only one single-axis gyroscopic sensor (yaw rate sensor), in general at least two measurements having to be performed in respectively different azimuth angular positions of a rotational axis of the sensor (relative to the base) using only one sensor.
For this purpose, EP 2 239 540 A1 proposes a gyroscope for use with a goniometer, the goniometer having an angle measuring sensor for determining the azimuth angular position. The gyroscope is provided to ascertain the north direction by means of two measurements in respectively one of two angular positions of the goniometer.
For high precision in the determination of a north direction from two measurements, is advantageous so set a defined relative angular position between the two measured positions, in which the influences on the sensor with the respective measurement can be ascertained as independently as possible and therefore precise determination of north can be performed. In this context, e.g., a first alignment of the structure and a second alignment relative to the first at an angle of, e.g., 90° or 120° are suitable, one measurement being performed by the gyroscope provided in the structure in each alignment. Since goniometers are typically provided in a robust embodiment without motorization, pivoting from the first angular position to the second angular position can be performed manually.
To achieve the respective, in particular advantageous angular position, a user can perform a respective required pivot of the structure relative to the base with the aid of information output on the device. It can be disadvantageous that graphically displayed information is at least partially concealed or can be moved out of the field of vision of the user upon pivoting of the structure into the respective measuring position, and therefore is not continuously available to the user until reaching the measuring position. Furthermore, it is disadvantageous that upon a corresponding rotation, the luminescent display changes its alignment so that it can be perceived by an enemy in direct line of sight and therefore a location of the goniometer is more easily recognizable. By arranging a display on the base (and therefore a fixed relative position to the base) of the goniometer, for example, the user could have the information continuously provided in one direction, however, it is disadvantageous in this case that the integration of the display in the base places a requirement on the installation space necessary for this purpose, which is to be avoided with respect to a compact device construction.
It is therefore an object of the present invention to provide an improved goniometer for providing defined and referenced azimuth angles, the device being designed for user-friendly, compact information output, which is particularly continuously perceptible to a user.
A further object of the invention is to provide an improved goniometer, which is equipped with an information output for robust, rapid, precise referencing of the device, which can be performed with high user-friendliness.
In addition, it is an object of the invention to provide information for initializing a goniometer so that during an initialization procedure of the goniometer, a direct visual connection between a graphic information output and an enemy is avoided.
A special object of the invention is to provide an improved goniometer with the capability of simpler and more user-friendly finding of north.
These objects are achieved by the implementation of the characterizing features of the independent claims. Features which refine the invention in an alternative or advantageous manner can be inferred from the dependent patent claims.